Method of deasphalting and dewaxing hydrocarbon oils



M. B. cooKE T AL April V18 1939.

METHOD vOF' DEASPHALTING AND DEWAXING HYDROCARBON OILS Filed Feb. 21,1935 muv I N V EN TOR. Mad/72e E. 600k.:

Patented Apr. is, i939/ y mamon F DEASPHALTING AND Dawax- !NG mRooAnnoNons Maurice B. Cooke, Plainfield, N. J., and Earl Petty, Scarsdale, N.Y., assignors, by mesne assignments. to Sun Oil Company, Philadelphia.Pa., a corporation of New Jersey Application Februar-yar, 1935, 'seraiN. 'wie (ci. 19e-is) 14 Claims.

'Tl'iis invention relates to the deasphalting and dewaxing oihydrocarbon oils and more particularly to wax and asphalt removalprocesses wherein'a solvent having an anti-solvent effect on asphalt atnormal temperatures, on wax at low temperatures and a solvent eiiect onthe oil throughout the dewaxing temperatures is used to facilitate theremoval.

In the asphalt separation processes known in '.the art, liuueiiednormallygaseous hydrocarbons have been found to be efficacious as oilsolvents which will readily precipitate asphalt at a nor- -maltemperature of, ior example, 80 F. The separation of the precipitatedasphalt is most .16' commonly accomplished by gravity settling as abatch operation which operation depends for eiiiciency upon therequirement that the liquid be in a non-agitated state and the viscosityoi the solution be low in order that the eilect .of

'20 gravity may be made offuse to cause settling within a reasonableperiod of time. The volume 'of solvent necessary to accomplish this ishigh and this liquid burden is disadvantageous from the standpoint oisolvent recovery from the yex- I 86 tract oil phase and from the asphaltphase.

The separation of the wax from the deasphaltized oil with the samesolvents has presented similar diiculties and others oi a differentcharacter. In the dewaxing processes ofA the discon- 130 tinuous orbatch type, utilizing a normally gaseous solvent, it is necessary tochill the solution to temperatures below that at which crystallizationof the wax may take place. When auto-refrigf eration is practiced, goodcrystallization of the wax can only be o btain'ed at or below theboiling point of the liquid by bringing about a state of quiescence inthe liquid. In those cases where partial evaporation of the solvent hasbeen practiced, with attendant refrigeration effect, the crystals formedat higher temperatures are destrayed-by the boiling liquid and are onlyrecrystallized after bringing the liquid to rest at a temperaturepressure equilibrium below the 'l boiling point of the solvent. Withheat absorp- `45 tion by propane, agitation occurs and convectioncurrents are set up which dlstributethe heat to the entire liquid bodyresulting in a change of state which destroys by minute dispersion andre-solution the wax crystals formed. Therefore, to obtain completecrystallization of the wax from the solution, the entire solution mustbe sub-cooled Aconsiderably below the temperature at which al wax wouldhave been crystallized from a quiescent solution.

56 We have round that by carrying on the entire chilling operation byindirect heat exchange at pressures substantially above the equilibriumpres sure of the liquid during chilling, for example, 100 lbs. persquare inch, or more, the crystals can be developed in the state, or asof the state of a true liquid at temperatures elevated above thosecustomary where auto-refrigeration is practiced. It the operation ofsub-cooling by. evaporation is practiced, as in conventional processes,a refrigeration cost results which is out of line with that for othersolvents such as ethylene dichloride or acetone benzol, for example,where crystallizan tion takes place in a quiescent liquid phase atelevated temperatures above the boiling point of the solvent. Itauto-refrigeration is practiced it means that special evaporators andcontrol of concentration of the solvent is required in order' toestablish a crystal that will provide for suitable yields even attemperatures of 45 F., or lower, as is the case when propane, forexample, is used as the solvent.

From an analogous viewpoint, experiments with the conventionalcentrifuge using a liquefied normallyy gaseous hydrocarbon solvent, suchas propane, chilled to a temperature of, for example,

45 F.,that is, equilibrium temperature -at atmospheric pressure, havegiven negative results and indications. The heat of friction at the bowlwall resulting in a temperature rise will cause boiling oi the propaneand crystal destruction. If the material is sub-cooled to overcome thisboiling, the crystals become too firm and solid, resulting in a bowlcake difllcult to discharge. Even then, the friction may causeevaporation resulting in drying and hardening of the cake and at thesame tine. interfering with separation due to vapor disturbances inpassing through the liquid.

WeA have found that these disadvantages with respect to centrifugaloperation may be over.- come by conducting the centrifuging operationwhile maintaining the liquid being centrifuged under a pressuresubstantially above the equilibrium pressure oi the solvent in thesolution, for example, maintaining a pressure of 100 lbs. per squareinch on the solution at 0 to 20 F.

It is one object of our invention to provide a process for deasphaltinghydrocarbon oils with a a normally gaseous hydrocarbon solvent whichwill materially reduce the quantity ofsolvent required to effect theseparation. It is another object of our invention to provide a processfor deasphalting hydrocarbon oils' with a normally gaseous hydrocarbonsolvent which will materially reduce the time required to separate theasphalt from the oil.

It is a further object of our invention to provide a process, fordeasphalting hydrocarbon oils with a normally gaseous hydrocarbonsolvent which will permit rapid continuous separation of the asphaltfrom the oil by means of high speed centrifuges.

It is a further object of our invention to provide a process fordeasphalting hydrocarbon oils with a normally gaseous hydrocarbonsolvent in which the ease of separation is aided by the presence of avnon-miscible liquid. v

It is a further Iobject of our invention to provide a process fordewaxing hydrocarbon oils with a normally gaseous hydrocarbon solvent bywhich the wax separation may be made at temperatures substantially abovethose customary with such solvents.

It is a further object of this invention to provide a process fordewaxing hydrocarbon` oils with a. normally gaseous hydrocarbon solventwhich will permit continuous centrifugal separation of the ywax in aplastic form without vaporization of the solvent by friction against thebowl wall and hardening of the wax on the bowl wall.

It is a further object of our invention to provide a process fordewaxing hydrocarbon oils with a normally gaseous hydrocarbon solvent inwhich the wax crystals will be formed in the oil solvent solution in theabsence of boiling of the solution.

It is a further object of vour invention to provide a process forremoving wax and asphalt from a hydrocarbon oil by centrifugalseparation of these constituents from a solution of the oil in a`liquefied normally gaseous hydrocarbon solvent.

It is a still further object of our invention to provide a new anduseful combination of apparatus capable of carrying out the process ofdeasphalting and/or dewaxing according to our insired a non-miscibleliquid such as water and/or other emulsifying agent, the oil solventsolution then being pumped to an accumulator or pressuring chamber inwhich a pressure is maintained on the solution greater than the vaporpressure of the solvent at its temperature in the solution byhydrostatic means, or by a gas substantially insoluble in the liquid atthis pressure and'having a vapor pressure higher than that of thesolvent at the sametemperature.

to a high Speed centrifuge wherein a separation of anasphalt-water-solvent phase from the 'oilsolvent phase is effected. Thisseparating operation is carried on under a .pressure slightly reducedfrom that in the accumulator (say 10 lbs. per square inch reduction) topermit liquid iiow, 'the centrifuge still being subjected, however, to apressure greater than the equilibrium pressure of the solvent at thetemperature of the solvent The lsolution containing asphalt precipitatedby the solvent is then fed under this pressure directly in thecentrifuge by means of a gaseous uid substantially insoluble in theliquid and having a vapor pressure higher than that of the solvent atthe same temperature.

The asphalt phase is discharged by gravity from the centrifuge into areceiver maintained under the same pressure as exists in the centrifugeby means of the same gaseous iluid acting through an equalizing manifoldconnecting the receiver and centrifuge. This pressure is lower than the-pressure in the accumulator fromwhich the solution is fed to thecentrifuge. The asphalt phasel is withdrawn from this receiver, pumpedto a separator still wherein the solvent is distilled from the asphaltand returned to the sol-4 'vent feed tank, while the water or otheremulsifying agent separated from the asphalt by the distillationoperation is returned to the nonmiscible liquid feed tank. The asphaltfree of emulsifying agent and solvent is withdrawn from thel separatorstill and pumped to storage.

The oil-solvent phase, discharged from the centrifuge, flows by gravityinto a separate receiver whose contents are maintained under the l samegas pressure as exists in the centrifuge and the asphalt phase receiverby means of the equalizing -manifold. The oil solution in this receiveris continuously withdrawn therefrom by means of a level-controlledmetering pump, diluted with additional solvent if necessary and thenpassed at a pressuregreater than the equilibrium pressure of the solventduring passage, through a series of indirect heat` exchangers whereinthe solution is chilled to a'temperature sufllciently low to precipitateor crystallize the wax, the chilled solution then being passed to asecond accumulator or pressuring chamber Where the solution ismaintained under a pressure such.

' as has been previously described in respect to the first accumulatorbut somewhat lower due to the pressure drop through the exchangers andthe somewhat lower equilibrium pressure of the solution at the chilledtemperature.

The solution containing the crystallized wax is then fed under thispressure to a separate centrifuge wherein a separation of a wax solventphase from the oil solution is made. The centrifuge is also operated inthis case under a pressure greater than'the pressure of the solvent atits temperature in the centrifuge by means of a gaseous fluid having avapor pressure higher than that of the solvent at the same temperature.As in the case of the deasphalting centrifuge, however, this pressureis`slight1y reduced from that existing in the accumulator. The waxsolvent phase discharged from the centrifuge is permitted to ow undergravity into a wax revist ceiver maintained at the same absolutepressure vas exists in the centrifuge by means of an equal- A equalizingmanifold. The oil-solvent solution in this receiver is continuouslywithdrawn therefrom and pumped through the exchanger-coolers in indirectheat exchange with the asphalt-free oil-solvent phase upon leaving theexchangercooling water.

coolers ls passed to a separate still wherein the solvent vapors aredistilled from the oil under a pressure suiiicient to permitvliquefaction of the solvent vapors upon cooling with the available Thesolvent-free oil withdrawn from the still will be a substantiallyasphalt and wax-free oil of the desired low cold-test and color.

Any of-the light gas used las the pressuring medium which dissolves inthe oil-solvent solution during the centrifuging or other operationswill be distilled from the oil and wax with the solvent vapors and notbeing condensible at these temperatures and pressures is returned as agas under substantially its initial pressure to the pressure gas feedtank. This tank is connected by means of suitable piping, pressureregulators and equalizing manifolds to both centrifuges andl to thevarious oil and wax receiver and accumulators so that it is possible tomaintain through.-

out the entire wax asphalt separating system an absolutepressure on thecontents of the system greater than the equilibrium pressure of thesolvent at its temperature at any point in the systern and at the sametime provide for pressure 4 drop control interstage.

A refrigeration plant of any suitable design is provided to supply acooling medium for circulating through the exchanger coolers and lforspraying into the bowl and motor compartments of the centrifuge tomaintain the motor and bowl at a temperature suiiiciently low to inhibitany tendency lto-cause vaporization of the solvent from heating ,due tomovement of the operating parts. f

Referring now more particularly to the drawing, solvent propane iswithdrawn from the feed tank I where it is maintained as a liquid at apressure of about 150 lbs. per square inch and passed through a line 2to the metering charge pump .1, It is, however, within the contemplationof our invention to use other liquefled normally gaseous hydrocarbonsolvents, for example, butane, n-butane, isobutane, alone or incombination with each other, or with propane.

. The metering pump 1 discharges the solvent through 'the manifold 8into a mixing device 9 provided with, if desired, suitablemechanicallydriven agitating devices; or merely with baiiles (notshown). At the same time a hydrocarbon oil containing wax and asphalt iswithdrawn from a .feed tank I through a line Il and forced by means ofan oil metering pump I2 through a heater I3 of any suitable form to themanifold I. Similarly, a fluid such as water non-miscible with the oiland solvent and having emulsifying properties with the asphalt iswithdrawn from a feed tank I4 and passes through the line I5 to thewater metering pump I8 by which it is discharged into the manifold 8.The ratio of solvent to oil is such as will just cause precipitation ofsubstantially all of the asphalt content in the oil. This ratio will be,for example, in the case of a topped East Texas crude, 4 to 5 parts'ofsolvent to l part of oil.

Similarly, we have found that, in general, 1 part of water when added tol0 parts of the oil will materially aid in the separation of the asphaltfrom the oil. 'I'he solution formed in the mixer 9, which will generallybe at a temperature in the neighborhood of 80- F., is withdrawntherevi'rom through a pump suction line- I1 connected to the ,solutionmetering pump I8. A solvent makeup line I9, controlled by a valve 20,connects the solvent feed line 8 to the pump suction line I1 of themixer 8 in order that additional solvent may be added to the solution ifit is deemed necessary. The pump I8 delivers the solution which nowcontains precipitated asphalt as a iinely divided slurry to theaccumulator 200 in which a constant liquid level ismaintained by meansof a liquid level control device The accumulator 200, the upper portionof which formsa gas dome, is provided with a vent line 2i having apressure relief valve 22. A

Ipressure gas line 2l having a pressure regulator 24 connects theaccumulator 200 with a high pressxre gas line 25 leading from a pressuregas tank The tank 28 having a vent line 21 provided with a pressureregulator 28 serves as a storage means for a gaseous uid by which apressure may be maintained on the surface of the liquid in the1%ceiver200 greater than the equilibrium pres-y sure of the solvent inthe solution at the temperature of` the solution in the accumulator20|). In the practice of our invention where propane is utilized as asolvent, we prefer to use a normally gaseous hydrocarbon lighter thanpropane, such as ethane, for example.

If ethane is used, it is desirable that the pressure regulator 24 be soadjusted that a gas pressure of approximately 200 lbs. per square inchexisting in the tank 28 be transmitted through the lines 25 and 23 tothe contents of the accumulator 200. Generally speaking, it is de;sirable that the gas used be substantially insoluble in the liquefiedsolvent and that the pressure of the gas be substantially above theequilibrium pressure of the solvent at the solvent temperature whereverthe gas pressure is applied. Any gas, therefore, having a vapor pressurehigher than that oi' the solvent at the same temperature willbe suitablefor the practice. of our process. Alternatively, however, itis withinthe contemplation of our invention to subject the solution in theaccumulator to a hydrostatic pressure.

The oil solvent solution containing precipitated asphalt with whichlatter there is associated the non-miacible fluid, which appears to formwith the asphalt an emulsion providing an extended surface area, isforced under the pressure head in the accumulator 200 through the line29 intothe bowl lll of the centrifuge generally indicated as II.

'I'he centrifuge 3|, though in the main of conventional constructionwith the usual heavy component discharge chamber 32, light componentdischarge chamber 38, overflow chamber 84, bowl chamber v and motorchamber 38 containing motor 31 driving the bowl 30 through the shaft JIpassing through the bearing 39, is specincally constructed so as topermit the maintenance within its shell of a relatively high gaspressure. This pressure will be slightly reduced from that in theaccumulator 200 (say by l0 lbs. per square inch) to secure an effectiverate of iiow through the centrifuge. The motor may drive the bowldirectly as we have shown or be arranged exv ternally of the centrifugeand drive the bowl liquid, for exampleliquid propane, or a gasatmosphere. 'I'he bearing I8 through which the bowl driving shaft 88passes is so constructed as bo permit a certain amount of freedom ofmovepasses up through the channel formed by the bowl 38 and theseparator disc 49 and is collected in the heavy component or asphaltphase chamber 82. Theoll solvent solution free of asphalt passes upthrough the channel formed by the center tube 4I of the centrifuge andthe separator gas pressure which will be substantially above the disc 40into the light component or oil solvent collecting chamber 33 of thecentrifuge. The asphalt phase with which is associated the nonmisciblefluid forming with the asphalt an emulsion, discharges by gravity iowthrough the line 42 into an asphalt receiver 43, which is provided witha liquid level control device 44 serving to maintain a constant liquidlevel in the receiver 43. 'I'he asphalt is withdrawn through the line 45by means of a pump 46 controlled by the level controller 44 anddischarged through the line 4 1 into a separator still 48. Suitableheating means (not shown) are provided in this still and serve to stripthe solvent from the asphalt, the solvent vapors passing overheadthrough the line 49 to the condenser 50 wherein they are cooled andliquefied through the line I to the solvent feed tank l.

The emulsion of asphalt and water is also broken in the still 48, thewater being removed from the still through the line 52 by means of apump53 which returns the -water through the line 54 to the non-misciblefluid feed tank I4. The asphalt now free of solvent and water is removed,fromthe still through the line 55 and passed to storage tanks (notshown).

The light component which, in this case, will be the oil solventsolution' lfree of asphalt, is discharged from the chamber 33 and ispermitted to flow under the action of gravity through the line 56 into aseparate intermediate receiver 511 which is likewise provided with aliquid level control device 58 serving to vmaintain a constant liquidlevel in the receiver.

In the operation of this centrifuge.. it is necessary to maintain at alltimes on the contents a equilibrium pressure of the'solvent at itstemperature in the centrifuge. We have'accomplished this by providinganequalizing manifold 59 which is connected tothe overflow chamber 34 ofthe centrifuge by means of the line 60, to`

the light component collecting chamber 33 by means ofthe line 6i, to theheavy component collecting chamber 32,by means of the line 62, to thechamber 35 surrounding the bowl l30 by means of the line 63, and tomotor chamber 36 co by means of the line 64;, This manifold is alsoconnected by means of the line 65 to the oil solvent receiver 51, abranch line 68 joining the as' The manifold 59 has its upper portionjoined by means of a gas line 1| having a pressure regulator 12 with aline 13 connected to the section side of a gas compressor 14. Thecompressed gaseous iiuid discharged from this compressor passes throughthe line 15, cooler 16 and line 11 to a separator 18. This separatorserves to remove messes any solvent liquefied by the compression andcooling, the solvent being returned through the line 19 in which isinterposed a back pressure control valve 88 to the line 8l connected tothe solvent feed tank l. The light gas free of the solvent passes fromthe separator 18 through the line 82 to the light gas feed tank 26.

It will be observed that by means of the equalizing manifold 59connected through the line 1i to the pressure gas line 13, itis possibleto maintain the contents of the centrifuge 3| and the contents of thereceivers 43 and 51 under the same absolute pressure. This may becontrolled by the pressure regulator 12 in the line 1I so that lthelight gas pressure in this system may be in the order of, for example,190 lbs. per square inch, which will be suillcient to prevent anyvaporization of the solvent in the centrifuge or in the receivers evenlwith-the slight pressure drop of say lbs. per square inch between theaccumulator and receivers.

The asphalt-free oil solvent solution is dis-- line 83 through the line86 in which is located the valve 81. The iow through either the pump 84or by-pass line 86 iscontrolled in either case, however, by the liquidllevel control 58 in the receiver 51. Additional solvent may be added tothe solution in the line 85 by means of thev line 88 throughmanipulation of the valvel 89. Solvent for this purpose is forced undera pressure of approximately 200 lbs. per square inch through the line 88by means of the pump 3 Whose discharge is controlled by the pressureregulator 4, the suction side of the pump being connected to the solventfeed yline 2 by means of the line 5. The -diluted solution then passesunder this pressure through the line 90 to a ilrst group of indirectexchanger coolers 9| from which the partemperature during the chilling.Since noy vaporization of the solvent can occur under these conditions,complete final crystallization of substantially all of the wax in theoil is secured with a final temperature considerably above thatnecessary where auto-refrigeration is used as a mode of chilling sinceno boiling ofthe solution with attendant crystal destruction occurs.This nal temperature usually will lie between -2 F. and 0 F. v

The chilled mixture of crystallized wax and oil solvent solution leavesthe tlnal coolers 93 through the'line 94 and passes to an accumulator 95wherein a constant liquid level is maintained by means of the liquidlevel control device 96. iThe upper portion of the accumulator 95 isconstructed to provide a gas dome above the liquid level and isconnected by means of a line 91 in whichis located a pressure regulator98 to the high pressure gas line 25 joining the pressure gas tank 26.I'he pressure regulator 98 will usually be adjusted to permit themaintenance of a gas pressure within the accumulator 95 of 100 lbs. .persquare inch when ethane is used as the4 pressuring medium ,and propaneis used as a solvent. It will be observed that a certain amount ofpressure drop, in thisl case about 90 lbs. per square inch, takes placebetween the receiver 61 and the accumulator 85 due to passage throughthe exchanger coolers and reduction in solvent vapor pressure as theresult of temperature decrease.

The oil-solvent solution containing the crystallized wax is deliveredunder the gas pressure head in the accumulator 95 through the line 99 tothe bowl (not shown) of theI dewaxing centrifuge |00. This centrifuge isanalogous to the deasphalting centrifuge 3| and the overiiow, lightcomponent, heavy component,'bowl and motor chambers are connected to anequalizing manifold |0.| by means 'of the lines |02, |03, |04, |05 and|06 respectively.

Each of the manifolds 59 and |0| is connected by means of lines |62 and|63 respectively to the pressure gas line 25 through pressure reducingvalves |64 and |65 respectively in order that pressures of 190 lbs. persquare inch and 90 lbs. per square inch respectively will be maintainedin these manifolds. e

The upper portion of the equalizing manifold is connected by means of aline |01 in which is located a pressure regulator |08 to the suctionside of a low stage compressor |09 whose pressure side is connected bymeans of the line 13,

as has been previously pointed out, to the suction side of the highstage compressor 14. Liquid collecting in the bottom of the manifold |0|is maintained at a constant level by means of a liquid level controldevice ||0 while the liquid which accumulates and which may be, forexample, cooling liquid such as brine, solvent, is withdrawn through theline III by means of the pump ||2and discharged from the line ||3 to arefrigerating plant generally indicated as ||4.

medium such as brine which is passed through the line ||5 and fed inwhole or in part, de-

'pending upon'the refrigeration load required,

through the line ||6 having a valve ||1 to the final coolers 83 fromwhich the cooling medium discharges through the line ||8 and returnstothe refrigeration plant ||4. A' portion of the cooling medium from theline ||5 may be passed through a branch line ||9 having a valve |20 andutilized as a cooling means for controlling temperatures in the bowlchamber oi.' the centrifuge |00 through the line |2| in which is locateda control valve |22. Similarly, a portion of this cooling medium may beutilized as a cooling means for controlling the temperature of the motorofthe centrifuge |00 through the line |23 having a control valve |24. Bythis means we are enabled to prevent any temperature rise of the bowl ormotor during operation and thus control any tendency to vaporization ofthe solveut which might otherwise exist as the result of heating due tofriction. Any liquid which accumulates in the base of the centrifugewill flow through the equalizing line |06 to the equalizing manifold |0|from which it may be returned ilzhiiough the line ||3 to therefrigeration plant The light component which in this case is thewax-free oil solvent solution is discharged from the centrifuge throughthe line |25 and ows under gravity into the receiver |28 provided with aliquid level control device |21 serving to mainf tain a constant liquidlevel in the receiver whose lupper portion is so constructed as toprovide a gas dome above the liquid contents. The oil solvent solutionis withdrawn from the receiver |26 through the line |28 and dischargedby means of the pump |29 through the line |30 to the rst group ofexchanger coolers where by indirect heat exchange it serves to extractheat from the Warm oil solvent solution undergoing chilling. Thewax-free oil solvent solution issuing from the coolers 9| passes throughthe line |3| and is delivered under the pressure of the pump |29 or anaxuiliary booster pump |80 into a still |32.

The still |32 is operated under a pressure of, for example, 250 to 300lbs. per square inch maintained by a pressure regulating valve |33 inthe vapor discharge line |34, the pressure being built up by the.solventvapors distilled from the oil as the result of heat exchange from aheating medium passing through a closed coil |8| in the still, whichmediumy is introduced through the line |35 and removed through the line|36. The solvent vapors stripped from the oil issue from the stillthrough the line |34 and pass through a line |31 and coolers |38 whereinthe. temperature reduction of the vapors, due to the normal availablecooling water, is sufficient to liquefy the vapors, the liquid issuingfrom the cooler |38 and passing through the line |39 to a light gasseparator |40. In this separator any of the light gas which, at theexisting pressure and temperature, will not be liquefied, is removedthrough the line 25 and returned to the light gas pressure feed tank 26.The liquefied solvent passes from the separator through the line |4| andpressure reducing valve |66 which joins the line 8| returning to thesolvent feed tank.

The oil in the still |32 now free of solvent is withdrawn from the stillthrough the line |42 in which is located a valve |43 and is passed tostorage tanks (not shown) as an oil of the desired low cold test andcolor characteristics. The refrigeration plant 4 provides a cooling Theheavy component, which in this case is the wax-solvent phase, issuesfrom the centrifuge through the line |44 and ows by gravity into areceiver |45 provided with a liquid level control device |46 serving tomaintain within the receiver a. constant liquid level. 'I'he upperportion of' the receiver is constructed so as to provide a gas domeabove the liquid contents. The overflow chamber of the centrifuge isconnected by means of a line |41 to a sight glass |48 from which a line|49 leads to the receiver |45. A'

similar overflow line is provided for the asphalt centrifuge 3|.

The receivers |26 and |45 have their gas domes Joined by means of anequalizing line |50 while the gas dome of the receiver |26 is alsoJoined by means of an equalizing line |5| with the equalizing manifold|0|. It will be observed that by this construction there will bemaintained on the liquid contents of each of the receivers an absolutepressure of the same value as that existing within the interior of allparts of the centrifuge |00 and, as in that case, this pressure will beapproximately 90 lbs. per square inch, i. e., with say a 10 1b. persquare inch reduction for feed through the centrifuge or, moregenerally, a pressure greater than the equilibrium pressure of thesolvent at its temperature in each 'of the receivers |26 and |45.

The wax-solvent phase accumulating in the receiver |45 issuestherefromthrough the line |52 and is forced by means of the pump |53through the line |54 into a still |55 maintained at a pressure of from250 to 300 lbs. per square inch by means of a pressure regulator |56located in a solvent vapor discharge line |51. The vapor line |51 Joinsthe line |31 and the solvent vapors are cooled and recovered in liquidform for re-use as has previously been pointed out in the operation ofthe still |32. A heating medium is Isupplied to a closed coil |82 in thestill |55, being introduced to the coil through the line |58 and removedthrough the line |59.

The wax tree oi' solvent is removed from the l bottom of the stm |55through a une lso having a control valve |6| and is passed to storagetanks (not shown).

It will be observed that we have accomplished the objects oi! ourinvention and have provided a process depending upon uninterruptedsuper-imposed pressure (at all times greater than the vapor pressure ofthe solution being processed) for deasphalting and dewaxing hydrocarbonoils which will permit rapid continuous separation of asphalt and Wax bya centrifuging operation in which a liquefied normally gaseous solventis used.

`We have provided a process not dependent upon auto-refrigeration and inwhich the liquid burden of solvent is reduced over that required forsolvent obvious that various changes may be made in details within thescope of our claims Without departing from the spirit of our invention.It is, therefore, to be understood that our invention is not to belimited to the specific details shown and described.

Having thus described' the invention, what is claimed is: I i

1. A processy fpr removing asphalt ffrom hydrocarbon oilslcomprisingforming a solution oi' an asphalt containing hydrocarbon oil with anormally gaseous solvent in such proportion as to precipitate insolubleasphalt from the oil, passing the solution containing insoluble asphaltunder a pressure greater than the equilibrium pressure of the solvent atits temperature during ,passage to a separating zone and therecentrifugally separating the asphalt from the solution While maintainingon the contents of the separating zone a pressure greater than theequilibrium pressure of the solvent at its temperature in the separatingzone by means of a gaseous uid having a vapor pressure higher than thatof the solvent at the -same temperature.

2. A process for removing asphalt from hydrocarbon oils comprisingpassing a solution. of an asphaltl containing oil in a normallygaseoussolvent to a separating zone, said solution containinganon-miscible fluid and insoluble asphalt, and there centrifugallyseparating an asphalt phase from 'the solution while maintaining apressure on the contents of the separating zone greater than theequilibrium pressure of the solvent at its temperature'in the separatingzone by means of a. gaseous uid having a vapor pressure greater thanthat of the solventat the same temperature. v

3. A proce for removing asphalt from a hydrocarbon oil comprisingforming a solution of an asphalt containing oil and a normally gaseoussolvent in lsuch proportions as will precipitate asphalt from the oil,passing the solution conaisacaa taining insoluble asphalt toa'separating zone. subjecting the solution during its passage to theseparating zone to a pressure greater than the equilibrium pressure ofthe solvent at its temperature during passage to the separating zone andcentrifugally separating the asphalt from the solution in the separatingzone while maintaining a pressure on the contents of the separating zonegreater than the equilibrium pressure of the solvent at its temperaturein the separating zone by means of a gas having a vapor pressure higherthan the solvent at the same temperature.

4. The process of claim 3 including the step yof adding a non-miscibleiluid to the solution during the solution forming step.

5. The process of claim 3 in which propane is the normally gaseoussolvent and in which a gas having greater vapor pressure then propane atthe same temperature is used as the pressuring gas.-

6. A process for removing asphalt from a hydroca-rbon oil comprisingpassing to a separating zone'a solutiony of oil in a liquefied normallygaseous solvent, said solution containing insoluble asphalt existing asa ilnely divided slurry and being under a pressure greater than thee'quilibrium pressure of the solvent at the solution temperature,centrifugally separating an asphalt phase from the solution in theseparating zone while maintaining a pressure on the contents of theseparating zone greater than the equilibrium pressure of the solvent atits temperature in the separating zone by` means of a gas having ahigher vapor pressure than the solvent at thea distillation. zone,distilling the solvent from the asphalt and removing the solvent-freeasphalt from the distillation zone.

7. The process of claim 6 wherein the solution contains a non-misciblefluid physically associated with the asphalt slurry so as to provide anextended surface area, said uid being removed from the separating zonewith the asphalt phase.

'8. A process lfor dewaxing hydrocarbon oils comprising chilling asolution of waxy oil in a normally gaseous solvent .under a pressuregreater than the equilibrium pressure of the solvent at its temperatureduringy chilling to secure a mixture formed of a crystallized wax phaseand an oil phase, passing the chilled mixture to a separating zone, andthere centrifugally separating the wax phase from the oil phase whilemaintaining a .pressure on the contents of the separating zone greaterthan the equilibrium pressure oi the solvent at its temperature in theseparating zone by means of a gaseous iiuid having a higher vapor-pressure than the solvent at the same temperature.

A 9. A process such-as dened by claim 8 including the .step ofsubjecting the mixture passing to the separating zone to the pressure ofa gaseous fluid having a vapor pressure higher than the solvent at thesame temperature, said pressure being greater than the equilibriumpressure of.

the liquid at its temperature during passage to the separating zone.

10. A process for dewaxing hydrocarbon oils comprising passing asolution oi' waxy oil in a liquetled normally gaseous hydrocarbonsolvent in indirect heat exchange with a chilling medium.

maintaining a pressure on the solution during chilling greater than theequilibrium pressure of the solvent at itstemper'ature during chilling,passing the chilled solution containing crystaltion, passing the dewaxedoil solvent solution in indirect heat exchange with the waxy oilsolution being chilled to act as a chilling medium, passing the dewaxedoil solvent solution to a distillation zone, distilling the solvent fromthe oil and separately removing the oil and solvent vapors from thedistillation zone.

11. A process for improving the cold test and color characteristics of ahydrocarbon oil con- -taining asphalt and wax comprising forming asolution of the oil vin a normally gaseous solvent under a .pressuregreater than the equilibrium pressure of the solvent at its temperatureduring the solution formingstep, centrifugally separating asphalt fromthe solution, chilling the asphalt-free -solution under apressuregreater than the equilibrium pressure of the solvent at itstemperature' during the chilling operation to solidify wax containedtherein, centrifugally separating in said separating zone the solidiiedwax from the chilled solution, maintaining a pressure on the solutionduring the centrifuging `operation greater than the equilibrium pressureof the solvent at the temperature of the solution during each of theseoperations by means of a gaseous uidhaving'a vapor pressure higher thanthe solvent and removing an oil solution free o1' asphalt and wax fromthe wax centrifuging operation.

12. A process for improving the cold test and color of asphaltic and waxbearing oils comprising mixing an asphalt and wax bearing oil with onlya sufficient amount of a .normally gaseous solvent at such a temperatureas will precipitate substantially all of the insoluble asphalt from thesolution formed, passing the solution containing insoluble asphalt to aseparating zone, subjecting the solution during its passage to theseparating zone to a pressure greater than the vapor pressure of thesolvent at its temperature during passage to the separating zone,centrifugally separating in said separating zone the asphalt from theoil solution, passing the asphalt free solution under a pressure greaterthan the equilibrium pressure of the solvent at its temy perature duringchilling in indirect heat exchange with a chilling medium to causecrystallization of the wax ,at a relatively elevated -temperature,.passing the chilled solution containing crystallized w'ax to a secondseparating zone, centrifugally separating in said second separating zonea crystallized wax phase from the solution, maintaining a pressure onthe contents of the separating zones greater than the equilibriumpressure oi the solvent at its temperature during the separatingoperations by means of a gaseous uid having a vapor pressure higher thanthe solvent at the same temperature, separately removing the wax phaseand the wax-free oil solution from the wax separating zone, passing theWax-free oil solution to a distillation zone, distilling the solventfrom the oil solution and separately removing the solvent vapors and thewax-free oil from the distillation zone. 13. A process for dewaxinghydrocarbon oils comprising passing a solution of waxy oil in aliquefied normally gaseous hydrocarbon solvent in indirect heat exchangeWith a chilling medium, maintaining a pressure on the solution duringchilling gre'ater than the equilibrium pressure of the solvent at itstemperature during chilling, passing the chilled solution containingcrystallized Wax to a separating zone, maintaining a pressure on thecontents of the separating zone greater than the equilibrium pressure ofthe solvent at its temperature in the separating zone by means of a gashaving avapor pressure higher than the solvent at the same temperature,and centrifugally separating in said separating zone a crystallized waxphase from ythe oil solvent solution.

14. A process for improving the cold test and color of asphaltic and waxbearing oils comprising mixing an asphalt and Wax` bearing oil with onlya sufficient amount of a liquefied normally asphalt from the oilsolution, passing the asphalt-A free solution under a pressure greaterthan the vequilibrium pressure of the solvent at its temperature duringchilling in indirect heat exchange with a chilling medium to causecrystallization of the wax at a relatively elevated temperature, passingthe chilled solution containing crystallized Wax to a second separatingzone, centrifugally separating in said second separating zone I acrystallized wax phase from the solution, maintaining a pressure on thecontents of the separating zones greater than the equilibrium pressure.of the solvent at its temperature during the separating operations bymeans of a gaseous uid 'having a vapor pressure higher than the solventat the same temperature, and separately removing the crystallized `Waxphase and the dewaxed oil solution from the wax separating zone.

MAURICE B. COOKE. EARL PE'ITY.

